This is an area of Linux where I still have an issue, and thats the sound output always reverting after every reboot, never could find the right command to fit it. POP OS is built off of Ubuntu just like Zorin OS is, and both share the common thread of Gnome as well.
But I have an extension installed that allows me to change the audio output from the top right menu. So its easy to set mine to HDMI that way. But yes, I do agree, the system should never be reverting like that, it just should simply remember what you set it to, and no longer be an issue.
Thats why I never once said that Linux was perfect. Linux most certainly has its issues, thats for sure. But in the 6+ years that I have been using it, IMO, its far better then Windows.
MS likes to make you give up a lot of freedoms to use its software, which provides you many conveniences. Of course I say that now, cause my past experience ended with Win7. Everything I hear about Win10 and now Win11, nobody talks about convenience, they are talking about pain in the butt.